1. Field of the Invention
This invention relates to a process and to the products produced thereby. More specifically, this invention is directed to a process for the in situ generation of high purity ceramics on a variety of substrates. The starting materials utilized in this process comprise a polymer film which has been formed by R.F. plasma vapor phase polymerization of a monomer comprising inorganic or organometallic constituents. The conversion energy is supplied by selective exposure of the film to a coherent or focused energy source of the appropriate power output and wavelength and for the appropriate duration.
2. Description of the Prior Art
The methods for formation of ceramic powders and objects are well known to the prior art. The formation of a ceramic object is usually preceded by mixing a blend of refractory powders of varying particle sizes, the compression of the refractory mixture into a "green" body and the controlled firing or sintering of the green body for a prescribed interval. The resultant object will generally be porous and its physical properties characteristic of a ceramic.
The prior art also discloses the preparation of sinterable ceramic powders from reactant gases which are rapidly heated by a CO.sub.2 laser, see Cannon et al, J. Am. Ceram. Soc. 65, pp. 324-330 (1982); and Cannon et al, Ibid., 65, 330-335. This article describes the decomposition of the reactant gases, thus, causing particles to nucleate and grow rapidly. This process reportedly permits the formation of ceramic particles essentially free from defects. This vapor phase method is reportedly superior to the more conventional furnace, R.F.-heated and arc-plasma-heated gas-phase synthesis techniques because of their less than ideal thermal profiles and because of the reaction zones of the equipment do not allow for distribution in nucleation rates and growth times.
The prior art also discloses the preparation of ceramic coatings from R.F. plasma polymerized polymer film, C. L. Beatty, "Silicon Nitride and Silicon Carbide from Organometallic and Vapor Precursors: Ultrastructure Processing of Ceramics, Glasses and Composites", editor Hench, et al, Chapter 23, pp. 272-292, John Wiley & Son (New York, 1984). The Beatty paper also describes the conversion of such coatings to ceramics by conventional pyrolysis techniques. Unfortunately, the resultant ceramics produced by such techniques were contaminated with carbonaceous inclusion or oxygen and, thus, did not possess the degree of purity required for electronics components or other applications where crystalline purity is a must.